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The Day Earth Survived the Greatest Stellar Attack, Ever

It came suddenly from the distant reaches of the Constellation Sagittarius, some 50,000 light years away. For a brief instant, a couple of tenths of a second, on December 27, 2004 an invisible burst of energy the equivalent of half a million years of sunlight shone on Earth. Many orbiting satellites electronics were zapped and the Earth’s upper atmosphere was amazingly ionized from a massive hit of gamma ray energy.

The source of the invisible attack was a rare magnetar SGR 1806-20 on the other side of the Milky Way. These soft gamma ray repeaters, SGRs, occur when twisted magnetic fields attempt to realign themselves and crack the magetar’s crust releasing the awesome burst or pulse of energy with a death zone of a few light years. Magnetars have magnetic fields 1000 times those of ordinary pulsars — so powerful as to be lethal at a distance of 1000 kilometers.

Atronomers have catalogued well over 1000 pulsars, and estimate the number of quiet neutron stars to be vastly more at some 100 million given the 10-billion-year life of the Milky Way’s disk. The odds are that one is nearby, gliding sliently past Earth, of no danger. The tinest fraction of neutron stars have morphed into magnetars, believed to be the offspring of the most massive stars, hypergiants that don’t have enough mass to evolve into black holes.

Fortunately for Earth, the nearest GRB candidate seems to be thousands of light-years away. Maybe…

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